This invention relates to selenium rectifiers and to a method of making them.
A conventional selenium rectifier consists of a metal plate, which acts as the rectifier base electrode, upon one side of which there are deposited, usually by evaporation techniques, layers of selenium with either a halogen additive, such as chlorine, or doped with a metal such as gallium or indium, or both an additive and a dopant. These layers of selenium may be sandwiched with relatively thin layers of various metals such as nickel between the selenium and the base electrode. The counter electrode is generally an alloy such as a cadmium tin alloy. Rectification takes place in a barrier layer which is adjacent the counter electrode. Such rectifiers are reliable but the evaporation apparatus is costly to install and maintain.